Process for preparing alkyldihalostibine



Patented Apr. 28, 1953 UNITED. STATES es PBJDCESS' QFORFPREPARING 'IALKYLDI HALQSTIBINE:

Mar;

Secretary. pfiWiim :2-

I Klimschi Chicago 1113, and: "Sidney- Paig assig'nors to tli" Unitedstatescof America as'representeiby. the.

a"will"mimber ,1952; Divided end-r thi's laplliitioh May. =15, 1952;SeriaiNiL29L054. .1

2 Claims.

The invention-describedhreiri may be menufaictured-and used byorforthe Government to -.1 governmental purposes without 1 the -paymenttto us-of anyroya'lty thereon;

This application-" ie -24 "division ofnourx-origirial This'invcntioti reldte'stda method tenths-preps oration ofethyldichlotoersinezand related organo mineral-halides;

An 1 object of: 'this eiriventionuis to: .Lpr'oVid'e: 1.2.

method for securinghigh yields of the desired product and which is*-we11-"suited for industrial scale manufacture.

Ethyldichloroarsine was introduced as e chem ioalrwerfareegent by the.Germensiinl lfi. The

best ,known methods foirpi epai'in-gethiscompoundhave been essentially the same as the German process: They; are complicatedand "involve the following steps: (1-). the conyersionoi ethyl chlo'rn ide into disodium ethyl*ensenete; ..(2)l.ithe,reducetion': of disc dium rethyl arsenate with. sulfur 1 .di-

oxide to form ethyl arsenious oxide; (3): thetreatment of ethyl arsenious oxide withhydrogen chloride to form ethyldichloroa-rsine. It has been confirmed that'this IJLOCBSS-giVBS. an average overali: iyield. :of only: about? 27. to, 30 at the. mostt Ituis ;:evident that 3 such aprioiu methods: .-illsuited-forlargezscale operations. For this-.reason a, :new" and. radically different method'hes been-1 deveiopedr:

In: the-new 1 method =of: this .invention, :ethyldi- 1- chloroarsine is prepared byte. reaction oftarsenic.

trichloride with tetreethyl. =1eacl .;under.. .suitable.:

conditions.-

Theoretically, the oveizrall reectiorrie:

However; .it is impcistern; tot-note theta the reactions:

evidently takes place in two stagesze- Theifirst sta ge of the reaction is repi esentedlby the equation:

and proceeds spontaneously at room temperature...

onet temperatures below 50.9.0. ..At'-.tl'1ese-tempers.

aturesieven. an..excess of arsenictrichloride'i 9511s to... detachle .th'ird .ethyl 1-Iadicalzfrom .the. leads.

atom... D

Thesecond stage represented by;

atunesiabowe 90 r651;

*maintemedeat. 420 i1161iplgg'dtlqtgiqistillsulat:

The reactioiis'may carried-ioutiiin the Heel-2:- ence of suitablesolventst'and lJhG OVBIF-JB/H. reaction S. may abs-harried 'out inaith'e. absences f1" solventses. When low lcoilifig' "solvents are use, toniy th'ev. fir stzi stage occurs; butwhenxthei reaction is: carried-butt above 80 C.; either inuth'e presence: or ebsenceof: z a 'high-boilifig solventfe g4" nitrohenzene',s'-both .1". stages" proceed simultaneously) The ethyl ch10: ride formed in the se'oondsstageimaybe recovered "quantitatively-0y: chilling: the evolved gases::i.Pure1:-.=

Air issWept-out of. the. flelsk by passing drymitro' gen-lithrough; the 'glasskinle'titubewettached to the: dropping fuhnel. This tuhe' islzthe'n closed off with a. screw clamp: The flask is' pl'aced man oil bath heated to 100 C.; and after the arsenictrichlo' ridehesreached approximately thattemperature,

"a few cc. oftetraethyl lead is-a-ddedlrom the dron ping: lfunnel: to :the'. :stirred- .arsenic trichloridei: Thestaiit of. the: reaetion which ioccurs in. a .few 1 minutes; isiindiceted by clouding ofithe liquid and separation of a iwhit'eaprecipitates- A total of.:1,620

(5 moles) of tetlaethyl"leadw;is ithen acldeda through: the; droppingefunnel 1 atz -such Te. ratezthat the: reaction mixture is kept eentl a boiling; .Dur-t ing: thisaddition.ofitheteti'eethyl lead and for. one houn after the I addition: is. :complete, ustirrin'g is continued, and the oil bath is held at a tempera-"m tune ot=about 101F110? CiliAbout sevenihouesnin all is required for these operations.

Aftet. the-product; has :cooiedto.-about: room temperature,thefiasl: is. connected with a Cleisen. Sti11-;he2'd.: 1 The-productis. distilled. directlyfrom:

the react-ion mixture :at 75 mmsepressure. The. receiver; a 311K812?- round-fbottom: flesh; is 1.0011:- nected to a vacuum. pump throughe trapgkept-et --80% C. Duringtthe:distillation:the. -.oil..bath-"is 82-83 C. About 80% of the product distills over in four to five hours; the distillation of the remainder is slower because of the large amount of lead chloride in the flask. The process may be hastened by gradually reducing the pressure. About ten hours is required to distill over an amount equivalent to a 95% yield.

The density of the crude water-white product varied in four runs from 1.6735 to 1.6799 as compared to 1.6570 for the very pure material distilled through a column. Hence the distillate obtained as described is 95.5 to 97% pure. The impurity is arsenic trichloride. the boiling point of which is below that of ethyldichloroarsine. Fractionation through a column readily separates the two substances, and the arsenic trichioride may be recovered. The percentages thus obtained check well with the composition calculated from the density of the crude material.

The described method with slight modifications k which are apparent can be applied on a com-- mercial scale. On an industrial scale the crude reaction product may be separated from the precipitated lead chloride by filtration. This type of separation has .een successfully carried out. No difficulties were experienced in carrying out the method described with proper precautions in handling the materials and in removing fumes.

For the purpose of comparison, arsenic trichloride was treated with tetraethyl lead in a manner similar to that described except in using carbon tetrachloride as a solvent in the reaction mixture and treating the mixture for about twelve hours at approximately the boiling point of the solvent. The yield of ethyldichloroarsine by this I low-temperature preparation was only 69% if the first stage reaction. is used as a basis of calculation, and is only 46% if the over-all reaction is used. Similar results were obtained when benzene (boiling point of 78 C.) or ligroin were used as solvents and the reaction carried out at temperatures below 80 C.

In another investigation the proportion of arsenic trichloride to tetraethyl lead was in creased to four moles to one. Benzene was used as a solvent, and the reaction was carried out at below 89 C. The recovered arsenic trichloride amounted to 1.3 mole equivalent; the ethyldichloroarsine obtained was equivalent to two moles of arsenic trichloride. that at a temperature below 80 0., a large excess of arsenic trichloride was capable of removing only two ethyl groups from the tetraethyl lead.

In all reactions conducted at temperatures above 80 C., with or without solvent, where three moles of arsenic trichloride to one mole of tetraethyl lead were used, the yield of ethyldichloroarsine approached the theoretical. For example, in a preparation in which no solvent was employed, the yield was 96.5%.

The liquid collected by condensing gas evolved during the reaction had a molecular weight corresponding to that of ethylchloride and boiled at 12 C. The solid residue was almost pure lead chloride.

Anal; Calcd. for PbClz: Cl, 25.5. Found: (31. 25.8.

When an equimolecular mixture of diethylleaddichloride and arsenic trichloride was heated to 125 0., there was a vigorous reaction and ethyl chloride was evolved. The reaction mixture was distilled at 75 mm. The product obtained was ethyldichloroarsine in a yield of 75%.

Reactions similar to the one used in the preparation of ethyldichloroarsine may be used for These results show Rn-MXm wherein Rn represents organic radicals, such as alkyl, aryl, alkaryl or aralkyl radicals; M represents a metal, non-metal or semi-metal, such as arsenic, phosphorus or antimony; and Xm stands for halogen groups, generally chloride or bromide groups; the subscripts n and m being whole numbers which add up to the valence of the constituent M, which is three for the trivalent mineral. atom.

Preparations here described are those of (1) diethylchloroarsine (C2H5)2 AsCl; (2) ethyldichlorophosphine CzI-IsPClz and (3) ethyldichlorostibine C2H5SbCl2.

Example 2 product boiled at Wt-78 C. under 74 mm. pressure.

Anal; Calcd. for EtzAsCl: CI, 21.1. Found: Cl, 18.0.

The product is, therefore, mainly diethylchloroarsine with a small amount of triethylarsine.

The white residue from the reaction was washed with benzene; it weighed 419 The theoretical yield was 50.5%.

Anal: Calcd. for (C2H5)2 PbClz: Cl, 21.2. Found: Cl, 21.9.

Example 3 Ethyldichlorophosphine preparation: Phosphorus trichloride, 69 g. (0.5 mole) was placed in a three-necked fiasl; fitted with a dropping funnel, mechanical stirrer and a reflux condenser. While a slow stream of nitrogen was passed into the flask, 54 g. (0.16? mole) of tetraethyl lead was added. Reaction was extremely slow; there was no precipitation of lead until the mixture had been refluxed for two hours. The flask was heated in an oil bath at 116 C. until the mixture ceased to reflux (36 hours). The volatile material was then distilled directly from the reaction vessel. The 58.5 g. of colorless, evil-smelling distillate (B. P. 94-91 C. at 760 mm.) represents a yield of 89 per cent.

Anal; Calccl. For CzI-IsPClz: Cl, 54.2. Found: Cl, 56.2, 56.1

Erra-mple 4 Ethyldichlorostibine preparation: In the apparatus for preparing' ethyldichloroarsine, 68.4 g. (0.3 mole) of dried and pulverized antimony trichloride was suspended in 160 cc. of solvent. Tetraethyl lead (32.3 g., 0.1 mole) was then added slowly. The mixture was heated under refiux for eight hours and then cooled. After the solvent had been removed by distillation, the residue was distilled under reduced pressure. The product which boiled between 113 and C. at 25 mm. was redistilled. A total of 48.6 g. of a colorless liquid was obtained (B. P. 62-83 C. at 1 mm., D 2182).

Anal: Calcd. for EtSbClz: C1, 31.95. Found: 31.40.

In these preparations a halide of a trivalent mineral constituent is treated with an organelead compound under conditions that are properly controlled to bring about replacement of the desired number of halogen constituents in the halide by organic radicals. To obtain proper control of the reactions, it is advantageous to heat the halide under reflux and to control the rate of reaction by the rate of addition of the organo-lead compound. The control is important for allowing the reaction to be brought up to the proper high temperature level. It has been shown that desired products are not obtained in satisfactory yields unless the reaction is carried out at a proper temperature level.

At a sufficiently high reaction temperature level, which may vary with the reactants and is in a number of instances of the order of 90 C. and higher, the organo-lead compound, represented by PbRs or RzPbXz, B being a hydrocarbon radical and X a halide radical, tends to be reduced to PbXz, the dihalide. Thus, likewise, at a sufficiently elevated reaction temperature, a PbRd compound, such as tetraethyl lead, is made to lose more than 2 R. (hydrocarbon) radicals from a molecule.

The organo-mineral-halides, and particularly the organo-mineraldihalides in which the mineral constituent is trivalent, have important uses as chemical warfare agents. In some instances the organo groups may be methyl or phenyl radicals for greater effectiveness. In the event the organo-metal halides lack the desired viscosity of persistency, they may be used together with suitable thickening agents. For example, ethyldichloroarsine may be blended with cellulose acetatebutyrate. A 5% solution of this type is comparable in consistency to glycerine and is quite stable. In addition to increasing the viscosity of the agent, a thickening additive may aid in lowering the volatility. The organo-minoral-halides may also be used in mixtures with other toxic agents.

It is to be understood that modifications may be made which come within the spirit and scope or the invention.

We claim:

.1. A method of preparing ethyldichlorostibine which comprises reacting antimony chloride heated under reflux with slowly added tetraethyl lead at an elevated temperature sufficient to form lead dichloride.

2. A method of preparing allcyldihalostibine which comprises reacting an antimony halide with a tetraalkyl lead at a temperature above 99 C.

MCRRIS S. KI-IABASCH. SIDNEY WEINHOUSE.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Kharasch et a1 Oct. 21, 1952 Number OTHER REFERENCES 

2. A METHOD OF PREPARING ALKYLDIHALOSTIBINE WHICH COMPRISES REACTING AN ANTIMONY HALIDE WITH A TETRAALKYL LEAD AT A TEMPERATURE ABOVE 90* C. 